JP2005121467A - Method for evaluating adhesion property of thin film, and method for manufacturing base having thin film on surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for accurately and rapidly evaluating the adhesion properties of a thin film formed on the surface of a material. <P>SOLUTION: The method for evaluating the adhesion properties of the thin film comprises a process for irradiating a sample surface having the thin film on the surface with electron rays with a specified acceleration voltage that is selected according to the film thickness for measuring the number of secondary electrons (1); a process for testing the peeling of the sample (2); a process for irradiating the sample surface after the peeling test with electron rays by the specified acceleration voltage for measuring the number of secondary electrons (3); a process for determining the difference between the measured value of the number of secondary electrons before testing peeling and that of the number of secondary electrons after testing the peeling (4); and a process for evaluating the adhesion properties of the thin film from the difference between the measured values of the number of secondary electrons before and after testing the peeling (5). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for accurately and quickly evaluating the adhesion of a thin film formed on a material surface and a method for producing a substrate having a thin film on the surface.

  In many technical fields such as surface treatment technology for steel products and chemical products, semiconductor products, recording and display related products, etc., the thin film application technology and the thin film control technology are the key to the development of characteristics. That is, the characteristics, physical properties, film thickness, and distribution of a thin film having a thickness of several angstroms to several hundreds of nanometers on the surface of the substrate are often the performance controlling factors. It is no exaggeration to say that the more important the thin film technology is, the more the evaluation technology becomes the key to product development, inspection and management.

  In the properties of thin films, the adhesion is one of the very important properties. If the adhesion is poor, it will lead to corrosion through peeling of the thin film and peeling, and the performance of the product will be significantly impaired. Therefore, a method for evaluating the adhesion of the thin film is important.

  The method for evaluating the adhesion of the film is, for example, a mechanical method such as a scratch test or an abrasion test, or the tape is once attached to the sample and then peeled off to quantitatively analyze the film constituent elements adhering to the tape. There is a tape peeling test. The latter includes a method of performing a tape peeling test after processing (for example, 90 ° bending or a draw bead test) in order to evaluate adhesion during processing. Also included in this is a method such as JIS K5400, in which crosscuts are put in a grid and the number of peeled grids is counted. More macroscopically, there is a shear tensile test of the bonded portion.

  However, the above method is a method for evaluating the macroscopic adhesion of the film, and it is difficult to evaluate the film adhesion of a minute portion and the film having a thin film thickness of about several tens of nanometers.

  Nowadays, materials and parts have a micro structure, and composite materials that combine multiple materials with different materials, shapes, etc., have come to be used. Although it has become necessary to evaluate the property, the aforementioned evaluation method is not suitable for the purpose. That is, the existing method can only evaluate the macro part including the film adhesion of the part that is originally desired and the film adhesion of the other part.

  In addition, without detailed study of the sample after the peel test, what kind of film peeling occurs, how the distribution of the peeled part is distributed, etc. It is difficult to obtain important knowledge to do.

  Furthermore, the conventional method requires a long time for the test. In the tape peeling method, since it is necessary to perform a quantitative analysis after the peeling test, the result is not quickly obtained. For this reason, not only can product delivery inspection and feedback to manufacturing conditions be performed efficiently, but also the speed of research and development is slowed down.

  The more important point is that when the film becomes thinner and the film is applied to a small amount of area, the mechanical method becomes difficult to apply, and the tape peeling method reduces the peeling amount itself. The accuracy of quantitative analysis becomes a bottleneck, and accurate evaluation becomes difficult. The mechanical peeling method includes a nano scratch test using a scanning probe microscope, but requires skill in measurement and interpretation of results, and can be applied only to a highly smooth substrate such as a silicon wafer or a hard disk. It is difficult to apply a sample having irregularities on the surface. The tape peeling method requires an enormous sample area to increase accuracy and is not practical.

  Further, in the tape peeling method, there is a problem that the substance adhering to the tape is not necessarily a film substance. For example, there is a high possibility that a part of the base peels off and adheres to the tape, or impurities present on the sample surface adhere to the tape and the amount of the peeled film is excessively estimated.

  As described above, there is a need for a technique that can evaluate the adhesion of a thin film at a specific portion of the target material, including the distribution of thin film peeling, and can be performed quickly. In addition, a method capable of evaluating the adhesion of the thin film to a non-smooth substrate is required.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for accurately and quickly evaluating the adhesion of a thin film formed on a material surface.

  The features of the present invention that solve the above problems are as follows.

The first invention is (1) a step of irradiating a sample surface having a thin film on the surface with an electron beam at a predetermined acceleration voltage selected according to the film thickness, and measuring the amount of secondary electrons;
(2) a step of performing a peel test on the sample;
(3) irradiating the surface of the sample after the peel test with an electron beam at the predetermined acceleration voltage and measuring the amount of secondary electrons;
(4) A step of obtaining a difference between a measured value of the amount of secondary electrons before the peel test and a measured value of the amount of secondary electrons after the peel test;
(5) A step of evaluating the adhesion of the thin film based on the difference in the measured value of the amount of secondary electrons before and after the peel test;
It is the evaluation method of the adhesiveness of a thin film characterized by having.

In the second invention, (1) a sample surface having a thin film on the surface is irradiated with an electron beam at a predetermined acceleration voltage selected according to the film thickness, the secondary electron image is observed, and the amount of secondary electrons is determined. A process of digitizing the brightness value of secondary electrons,
(2) a step of performing a peel test on the sample;
(3) The surface of the sample after the peel test is irradiated with an electron beam at the predetermined acceleration voltage, the secondary electron image is observed, and the secondary electron quantity is quantified as a brightness value of the secondary electron quantity. Process,
(4) obtaining a difference between the brightness value of the secondary electron amount before the peel test and the brightness value of the secondary electron amount after the peel test;
(5) a step of evaluating the adhesion of the thin film based on the difference in brightness value of the amount of secondary electrons before and after the peel test;
It is the evaluation method of the adhesiveness of a thin film characterized by having.

  According to a third invention, in the first invention, the electron beam irradiated on the sample surface is irradiated while scanning the sample surface, and the amount of secondary electrons corresponding to the electron beam irradiation position before and after the peeling test is obtained. Measure the adhesion of the thin film at each position on the sample surface from the difference between the measured values of the secondary electron quantity before the peel test and the secondary electron quantity after the peel test corresponding to the electron beam irradiation position. It is the evaluation method of the adhesiveness of a thin film characterized by these.

  According to a fourth invention, in the second invention, the electron beam irradiated on the sample surface is irradiated while scanning the sample surface, and the amount of secondary electrons corresponding to the electron beam irradiation position before and after the peeling test is measured. Each brightness value is obtained, and the difference between the brightness value of the secondary electron quantity before the peel test corresponding to the electron beam irradiation position and the brightness value of the secondary electron quantity after the peel test at each position on the sample surface. A method for evaluating the adhesion of a thin film, comprising evaluating the adhesion of a thin film.

  A fifth invention is a method for evaluating adhesion of a thin film according to any one of the first to fourth inventions, wherein the acceleration voltage of the electron beam applied to the sample surface is in the range of 0.01 kV to 2 kV. .

  A sixth invention is a method for evaluating adhesion of a thin film according to the first to fifth inventions, wherein the thin film is made of an oxide and / or hydroxide on a metal or a semiconductor.

  7th invention is the manufacturing process which forms a thin film on the surface of a base material, and the base material which formed the thin film on the surface by the said manufacturing process in any one of 1st-6th invention with respect to one part or all. And a method for producing a substrate having a thin film on the surface thereof.

  The eighth invention, in advance, to determine the correspondence between the difference between the amount of secondary electrons before and after the peel test and the adhesiveness or the difference between the brightness value of the secondary electron amount before and after the peel test and the adhesiveness, The evaluation process includes a correspondence relationship between the difference in secondary electron amount before and after the peel test and adhesion, and a difference in measured value of the secondary electron amount before and after the peel test in the evaluation process, or two before and after the peel test. Whether or not the thin film has a predetermined adhesion, based on the correspondence between the difference in the brightness value of the secondary electron amount and the adhesiveness, and the difference in the brightness value of the secondary electron amount before and after the peel test in the evaluation step. This is a method for producing a substrate having a thin film on the surface according to the seventh invention.

  According to the evaluation method of the present invention, the adhesion of the thin film on the surface that influences many of the characteristics of the material can be evaluated more simply, more quickly and more accurately than existing methods. According to the evaluation method of the present invention, by using an extremely low acceleration voltage, it is possible to cope with the adhesion evaluation of an ultrathin thin film having a thickness of about several nanometers, which is difficult to evaluate with existing technology.

  In addition, according to the evaluation method of the present invention, it is possible to evaluate the adhesion at a minute site, so it is possible to accurately evaluate the adhesion of a thin film formed on a non-smooth surface or a thin film at a specific site of a material. it can.

  When forming a thin film on the substrate surface, the adhesion of the thin film is evaluated by the method of the present invention, and based on the result, appropriate product management and shipping management become possible as well as product development. Also, the evaluation result can be fed back to the manufacturing process for forming the thin film and used for adjusting the manufacturing conditions.

The present invention will be described in detail below.
The features of the present invention are (i) that many of the important films on industrial products have low conductivity, and (ii) the difference in secondary electron emission rate between the film material and the base material with respect to electron beam irradiation. Paying attention, (iii) is to detect the presence or absence of the film as a difference in the change in secondary electron emission rate with respect to a constant acceleration voltage. However, as will be described later, the condition of (i) is not essential as long as there is a difference in the amount of secondary electrons emitted between the coating substance and the base.

  The inventors have found that there is a great difference in the brightness of the secondary electron image depending on the presence or absence of a low-conductivity film while examining various thin film samples using the ultra-low acceleration SEM technique. This difference in brightness (hereinafter referred to as contrast) is considered to be caused by the mechanism schematically shown in FIG. 1 in the case where an oxide layer having low conductivity exists on a metal.

  That is, at the normal acceleration voltage, as shown in FIG. 1A, secondary electron emission from the base material is dominant in both the portion with the film material and the portion without the film material. Therefore, the difference in the amount of secondary electron emission between the portion with the film material and the portion without the film material is small. On the other hand, when the acceleration voltage of the incident electrons is selected under the condition that the diffusion of the electrons after the incident is within the coating material, as shown in FIG. Secondary electron emission is determined by the film material itself, and the amount of secondary electron emission in the portion without the film material is determined by the base material itself. At this time, a difference occurs in the amount of secondary electron emission between the film material and the base. For this reason, a material contrast is generated due to a difference in material between the portion with and without the film material. When the film has a low conductivity, a portion where the film exists appears as a region having a small amount of secondary electrons, that is, a dark contrast.

  The inventors have found that the adhesiveness of the thin film can be evaluated using this phenomenon.

  That is, the sample before the peel test is irradiated with an electron beam at an acceleration voltage that causes a difference in the amount of secondary electrons between the film region and the base region as described above, then the peel test is performed, and the sample after the peel test is the same as described above. An electron beam is irradiated with an acceleration voltage, and a change (difference) in the amount of secondary electrons before and after the peel test is obtained. When a part of the film is peeled in the peel test, the film area is reduced and the area of the base is increased. Therefore, the amount of secondary electrons changes before and after the peel test.

  Based on the change in the amount of secondary electrons before and after the peel test, the difference in the coverage of the film, that is, the peel area can be obtained, so that the adhesion of the film can be evaluated.

  When evaluating the adhesion at a specific minute part or when evaluating the distribution in the surface of the peeled part, the incident electron beam is finely scanned to irradiate a specific part of the surface, corresponding to the electron beam irradiation position. To measure the amount of secondary electrons. That is, based on the principle of a scanning electron microscope (SEM), the amount of secondary electrons is recorded corresponding to the position on the sample. In this case, it is more accurate to observe the same sample and the same visual field before and after the peel test and to measure the difference in the distribution of secondary electrons. By measuring the distribution of the amount of secondary electrons between the two and obtaining the difference between them, the distribution in the surface of the part where the film peeling occurred can be known instantly, and the amount of secondary electrons at each point is evaluated. By averaging the specific area, the adhesion of the specific area can be evaluated.

  The above has been described with the case where a part of the thin film is peeled off in all layers, but it is conceivable that the thin film is not peeled off in all layers, for example, only the upper part of the film peels off. Even when such peeling forms coexist, the adhesion of the film can be evaluated as follows. The inventors have found that the amount of secondary electrons varies continuously in relation to the thickness of the thin film. As the film becomes thinner, the amount of secondary electrons increases and changes so as to approach the amount of secondary electrons of the base, so the change in the amount of secondary electrons in the entire field of view before and after the peel test, or secondary electrons averaged in a specific region It is possible to evaluate the in-plane distribution of the amount of peeling from the amount of film peeling based on the change in amount, and from the change in the amount of secondary electrons before and after the peeling test corresponding to the electron beam irradiation position.

  In the above method, the essence is the amount of secondary electron emission, but the brightness of the secondary electron image is measured using SEM, and it is converted into a numerical value. Can be evaluated. Quantifying and evaluating the brightness of the secondary electron image has the advantages of (1) being simple and (2) being able to easily obtain a two-dimensional distribution of film and thickness. (3) The surface morphology and composition distribution of the sample can be evaluated as necessary using various surface image observation functions and element analysis functions provided in the SEM.

  The acceleration voltage range of the electron beam irradiated in the present invention, that is, the acceleration voltage range in which the amount of secondary electrons is different between the coating region and the base region without the coating is determined by the thickness of the thin film.

  An example of a method for measuring and obtaining acceleration voltages with different amounts of secondary electrons depending on the presence or absence of a film is to accelerate by changing the acceleration voltage of the electron beam irradiating the sample from higher to lower or from lower to higher. In this method, changes in secondary electron generation amount (brightness of secondary electron image) with respect to voltage are evaluated, and acceleration voltages having different secondary electron generation amounts (brightness numerical values) depending on the presence or absence of a film are obtained.

  FIG. 2 shows a sample (2) to (4) having a thin film (here, an oxide layer) made of a material having a lower conductivity than that of the metal on the metal. It is a schematic diagram which shows the change of the amount of secondary electrons generated when it is changed to the lower side. The film thickness is sample (4)> sample (3)> sample (2). The amount of secondary electrons emitted from the surface of the sample (1) where the film does not exist is actually dependent on the acceleration voltage, and the amount of secondary electrons generated changes little by little when the acceleration voltage is lowered. However, in FIG. 2, the change is ignored, and the dependency of the amount of secondary electrons generated on the sample (1) having no coating on the acceleration voltage is shown by a straight line with a constant amount of secondary electrons generated.

  The acceleration voltage dependence of the amount of secondary electrons generated in the samples (2) to (4) having a low-conductivity film on the surface is a curve as shown in the figure. That is, in the region where the acceleration voltage is high, the change in the amount of secondary electrons generated is similar to that of the sample (1) in which the thin film does not exist even if the acceleration voltage is lowered. The amount of secondary electrons generated decreases significantly. This is because, as described above, the spread of incident electrons in the sample is limited to the inside of the film, so that the surface of the low-conductive film is positively charged and the amount of secondary electrons generated is reduced. Conceivable. In FIG. 2, the dependence of the secondary electron detection efficiency of the device on the acceleration voltage is ignored.

  An acceleration voltage at which the secondary electron generation amount deviates from the smooth curve and starts to decrease (indicated by ▽ marks in FIG. 2) is obtained, and the acceleration voltage at which the film thickness and secondary electron generation amount start to decrease is obtained. When the relationship is shown, a characteristic curve as shown in FIG. 3 is obtained. In the present invention, the acceleration voltage of the electron beam is selected from a region below the characteristic curve in FIG. 3 determined according to the thickness of the thin film.

  The method for determining the accelerating voltage range of the electron beam to be irradiated based on the measurement results has been described above. However, if the composition, composition, density, and film thickness of the film material are known, the Monte Carlo simulation etc. This can be determined by obtaining an accelerating voltage that limits the spread in the sample within the film. For the Monte Carlo simulation, commercially available Monte Carlo simulation software can be used.

  When the thickness of the target thin film is 1 nm or more and 50 nm or less, it is necessary to set the acceleration voltage to an extremely low acceleration voltage of 0.01 kV or more and 2 kV or less depending on the film material. For example, when the thickness of the thin film is 1 nm or more and 30 nm or less, an acceleration voltage of 0.01 kV or more and 1.0 kV or less is effective. When the thickness is 1 nm or more and 10 nm or less with a thin film, an acceleration voltage of 0.01 kV or more and 0.3 kV or less is effective.

  FIG. 4 shows the amount of secondary electrons generated in samples (2) to (4) at a constant acceleration voltage (acceleration voltage X in FIG. 2) selected from the acceleration voltage in the region below the characteristic curve in FIG. , A, b, and c, respectively, illustrating the relationship between the film thickness and the amount of secondary electrons generated. In FIG. 4, since the secondary electron generation amount corresponds to the film thickness, the film thickness can be evaluated by measuring the secondary electron generation amount with the acceleration voltage. Further, by utilizing this relationship, the film thickness before the peel test and the film thickness after the peel test are evaluated, and the difference between them is evaluated to evaluate the degree of film peeling, that is, the adhesion of the film. By obtaining the relationship between the amount of secondary electrons generated at a constant acceleration voltage as shown in FIG. 4 and the film thickness in advance, the film thickness of a sample with an unknown film thickness can be determined. As a result, it is possible to evaluate the film dropout and the adhesiveness not only in the case of peeling of all layers of the film but also in the case where the film thickness becomes thin due to destruction / desorption in the film. become.

  2 to 4 show examples of the relationship between the amount of secondary electrons generated and the film thickness, but the relationship between the brightness value and the film thickness can be obtained in the same manner instead of the amount of secondary electrons generated. .

  The present invention has been made based on the above findings. Based on the above findings, the inventors applied the thin film adhesion evaluation method of the present invention to a low-conductivity film on a metal or semiconductor, and confirmed that it is useful for evaluating the adhesion of the film. . The thin film adhesion evaluation method of the present invention can be used for product inspection and shipping quality control of these materials, and can also be applied to a manufacturing method incorporating the evaluation process, a method for correcting operating conditions, and the like.

  Hereinafter, the present invention will be described in detail by taking as an example the case of evaluating even the in-plane adhesion distribution based on the brightness value using SEM. When average information is sufficient for evaluating adhesion, the results can be simply averaged or evaluated with an unsqueezed beam, and the electron beam source that can irradiate the sample and the amount of secondary electrons generated from the sample are measured. It is possible to evaluate even a simple device having the function to do this.

  In the present invention, an appropriate constant accelerating voltage (an accelerating voltage that causes a difference in the amount of secondary electrons between a film region and a base region without a film) is previously obtained for a material having the same type of thin film as the material to be evaluated and having a different thin film thickness. The surface is observed with an SEM at an acceleration voltage selected from within the range, and after taking an image, the brightness is quantified and, for example, the relationship between film thickness and brightness is investigated as shown in FIG. And ask. The brightness of the sample without the thin film or the base portion (the portion without the thin film) is also investigated and determined. In FIG. 5, Bs is the brightness value of the background portion. However, this step can be omitted when the peeling mode of the coating is all-layer peeling and the adhesion can be evaluated by the presence or absence of the coating.

Next, a sample for adhesion evaluation is cut out from the material to be evaluated as necessary. Next, the cut sample is washed if necessary, the surface thereof is observed with an SEM at an appropriate acceleration voltage, an image is taken in, and the brightness is digitized. The sample is then subjected to a peel test. The method may be a tape peeling method, a tape peeling method after processing, or a mechanical abrasion test. It can also be applied to the evaluation of film adhesion due to corrosion by a method of immersing in a solution such as a corrosion acceleration test. After the peel test is completed, the sample is washed as necessary, the portion observed before the test is observed with the same acceleration voltage, the image is taken in, and the brightness is digitized. The difference in brightness before and after the peel test is obtained, and the adhesion of the thin film is evaluated from the result. That is, in FIG. 5, if the brightness before the peel test is B _F1 and the brightness after the peel test is B _F2 , the brightness B _F1 and B _F2 are the film thicknesses (if the film thickness is not uniform, Since it corresponds to t ₁ and t ₂ (which is the average film thickness), the difference in brightness B _F1 -B _F2 before and after the peel test corresponds to the film reduction t ₁ -t ₂ by the peel test. Therefore, the adhesion of the thin film can be evaluated based on the difference in brightness before and after the peeling test B _F1 -B _F2 (in the case of full-layer peeling, B _F2 = B _S ).

Further, since the film thickness t ₁ of the previous peeling test corresponds to the B _F1 -B _S, the remaining film thickness t ₂ after the peel test corresponds to the _{B F2 -B S, (B F2} -B S) / (B _F1 −B _S ) represents the film remaining rate after the peel test. Thereby, the adhesion of the thin film can also be evaluated.

  For the evaluation of adhesion, an SEM that can always stably irradiate an electron beam with an acceleration voltage of 2 kV or less can be used. In this acceleration voltage range, the acceleration voltage can be freely changed without losing the spatial resolution better than 5 nm, and it is desirable to have a Schottky field emission electron gun from the viewpoint of electron beam stability. As the secondary electron detector, one capable of selectively detecting low energy secondary electrons as much as possible is desirable. In addition, it is desirable to have a sample preparation room because it can set up up to measurement quickly. As an example, the LEO 1500 series and the SUPRA series (LEO) are suitable for the above purpose.

  The measurement of the amount of secondary electrons is a direct method of taking secondary electrons as a current, but it is easy to evaluate the brightness of the secondary electron image numerically. If the secondary electrons take in a lot of low energy secondary electrons, the change in the amount of secondary electrons accompanying the difference in conductivity can be measured efficiently.

In order to quantitatively evaluate the distribution of the film from the brightness obtained at a constant acceleration voltage, it is important to make the observation / image capturing and quantification conditions the same. In particular, when the same visual field is quantitatively evaluated before and after the test, it is necessary to compare the results obtained under the same conditions with respect to the inspection object. Capture images as digital data under the same conditions. In this case, the same observation conditions are as follows.
Acceleration voltage: Determined according to the target film thickness as described above.
・ Entrance electron conditions: acceleration voltage, aperture, beam diameter (normally minimum), electron scanning range (magnification), scanning speed (electron beam irradiation time per point), scanning method / detection conditions: detector conditions (applicable) Voltage, etc.), brightness, contrast / image capture conditions: number of capture points, capture time, brightness, contrast Next, the captured image is read by image processing software. This software can be self-made or commercially available. An example of the latter is Adobe Photoshop. On the software, the brightness of the image range excluding abnormal parts such as adhering matter is digitized. There is no limitation on the numerical method, but for example, the brightness is divided into 256 gradations.

When obtaining average information of the sample surface, a method of averaging with the number of image data points within the above range can be employed. For both the sample before the peel test and the sample after the test, the images are digitized in the same manner. Also, the brightness of the film-only region and the base-only region observed under the same conditions is digitized.
From these results, the coating rate of the film can be evaluated by equation (2).

This means that the brightness B _F of the film part, the brightness of the base part B _S , and the coverage of the film C, the overall brightness average value B and B = (B _F × C + B _S × (1− C)).

  The film coverage is obtained before and after the peel test. As shown in FIG. 5, since the overall average brightness value B corresponds to the film thickness, the film remaining rate, that is, the adhesion of the film can be evaluated from the equation (3).

  In addition, the film coverage in the formula (2) is a description assuming that all layers of the film are peeled off, but when the film thickness is thinned by a peel test, this is replaced with an average film thickness, The film remaining rate can be similarly evaluated.

  Here, it was described that the same field of view of the same sample was evaluated before and after the peel test. However, when the state of the film before the peel test is known, for example, the film covers the entire surface of the sample with a uniform thickness. If the distribution of the film or the film is uniform, once the secondary electron image brightness of such a film is evaluated, the adhesion can be evaluated simply by evaluating the surface after the peel test.

  In addition, as a simpler method, the brightness of the secondary electron image obtained under the same conditions is digitized, and the film part and the ground exposed part are binarized at an appropriate brightness (threshold value). The film residual rate can be evaluated by calculating the rate and using the equation (3). In this method, it is not necessary to measure the brightness of only the film and only the ground.

  In order to evaluate the adhesion of the specific minute portion, the equations (2) and (3) may be applied to the data obtained by averaging only the data of the specific region.

  In order to investigate the in-plane distribution of the degree of film peeling, the distribution of the brightness distribution ratio of secondary electron images before and after the peeling test (brightness value after peeling test / brightness value before peeling test or vice versa) By obtaining, the part which peeled can be visualized.

  The material targeted by the present invention has a thin film on at least a part of the surface of the base material (underlying substance), and the thin film is a material made of a conductive material lower than the conductivity of the base material. As a specific example, a material in which a film having a lower conductivity is present on a metal or semiconductor is an object of the present invention. In the semiconductor field, an insulating film or a dielectric film on silicon can be cited. Examples of the low conductive film include an oxide or hydroxide on a metal plate such as a steel plate, or a surface treatment film mainly composed of an organic compound or a polymer material.

  It is a good subject of the present invention that the properties of these products depend on the thickness of the low conductive film. The thickness of the target low-conductivity thin film is 1 nm or more and 1 μm or less. The present invention can be more suitably applied to a thin film having a thickness of 1 nm to 100 nm, and can be particularly preferably applied to an extremely thin thin film having a thickness of 1 nm to 10 nm.

  However, the present invention is not necessarily limited to the conductivity of the film, and can be applied as long as the amount of secondary electrons differs between the film material and the base material.

  Although the principle is different from that in FIG. 1, if the average atomic number of the film material and the base material is different, the backscattered electron detector is used to calculate the amount of reflected electrons due to the difference in the average atomic number of the film material and the base material. You can take advantage of the differences. This method is not suitable for ultrathin layers, but can also be applied when there is no difference in conductivity.

  According to the present invention, the adhesion of a thin film can be accurately and quickly evaluated. By applying the thin film evaluation method of the present invention to the material manufactured in the manufacturing process of forming a thin film on the surface of the substrate, it becomes possible to appropriately distribute the shipping destination of the material.

  That is, the correspondence between the difference in the measured value of the amount of secondary electrons before and after the adhesion test or the difference in the brightness value before and after the peel test and the adhesion is obtained, and the adhesion at which the adhesion of the thin film becomes a predetermined adhesion level. The threshold value of the difference in the measured value of the amount of secondary electrons before and after the property test or the difference in brightness value before and after the adhesion test is set in advance. If the difference in measured secondary electron quantity before and after the adhesion test or the difference in brightness value before and after the peel test obtained from the evaluation result of the thin film of the material manufactured in the manufacturing process is equal to or greater than the threshold value, the thin film Is determined to have a predetermined adhesion.

  The threshold value is used as a threshold value for determining whether or not the adhesiveness is acceptable. If the adhesion evaluation result of the thin film of the material manufactured in the manufacturing process is equal to or greater than the threshold value, the material is directed to a predetermined allocation destination. For example, the material can be prevented from being directed to a predetermined allocation destination.

  Further, the threshold value is set to a plurality of threshold values, for example, a high grade threshold value and a low grade threshold value, corresponding to the adhesion level, and the adhesion evaluation result of the thin film of the material manufactured in the manufacturing process Compared to each of the above threshold values, if the result of the adhesion evaluation of the thin film of the material is equal to or higher than the high grade threshold value, it is directed to a provision that requires high grade adhesion. However, if it is less than the low grade threshold value, it may not be assigned to any of the above.

  When the quality of the product can be determined by the coating rate of the film, it is effective to evaluate the coverage of the thin film in the product or prototype using the method for obtaining the coating rate described in this specification. By handling the obtained coverage of the thin film in the same manner as the above-mentioned adhesion, it is possible to inspect the product (evaluation of quality or grade sorting) and determine the manufacturing conditions in the manufacturing process.

Next, an example explains the present invention.
An alloyed hot-dip galvanized steel sheet was produced by a conventional method, and a flat portion was provided on the plated surface by temper rolling. The steel sheet was immersed in an acidic solution containing sodium acetate at pH 1 and then dried at 200 ° C., thereby forming an oxide layer mainly composed of Zn on the surface of the galvannealed steel sheet. Three types of oxide layers were formed by changing the content of sodium acetate. As a result of measuring with an Auger electron microscope, the oxide was formed only on the flat part produced by temper rolling, and the thickness of the oxide was all around 40 nm. This oxide layer was subjected to a peel test in which the acetylcellulose film was pressure-bonded to the sample surface through acetone for 30 seconds and peeled twice.

  Using the SEM (LEO1530), the sample surface was scanned at an acceleration voltage of 0.5 kV, and an image was captured as digital data. Image capture was performed for the same field of view before and after the peel test. From each image data, the average brightness of the flat portion was quantified. In addition, from the respective image data, regions of only the film existing portion and only the base portion were selected, and the average value of the brightness of each region was digitized. From these numerical values, the film coverage and the film remaining rate were determined from the above equations (2) and (3). The numerical value of the brightness was numerically expressed with 256 gradations using commercially available software Photoshop (manufactured by Adobe).

  Table 1 shows the results of quantification from the image data of samples A to C, and the results of evaluation of the film coverage and the film residual ratio before and after the peel test on the flat portion of the sample.

  It can be seen that Sample A has the poorest film adhesion among the three samples. Sample C has a lower film coverage before the peel test than other samples, but has the highest film residual rate (film adhesion rate) and a high film coverage after the peel test. Based on this result, it was possible to determine the conditions for forming an oxide film with high adhesion.

  As in this example, the present invention is particularly effective when the formation of the film is limited to a specific portion of the surface. For example, even if a quantitative evaluation can be made in the tape peeling test, the distribution of the film is not known, so the adhesion per unit area of the sample (average adhesion evaluation over a wide area) can be performed and formed on a flat part. The adhesion of the applied film cannot be evaluated.

  A threshold value was determined so that the film portion could be extracted from the same image data as described above, and binarization was performed based on the threshold value, and the change in the coating rate before and after the peel test was also examined. As a result, in Sample A, the remaining rate of the film was about 40%, which was the same result as described above. This shows that the adhesion of the film can also be evaluated by this method.

  6A and 6B are secondary electron images before and after the peel test of Sample A, (a) is the secondary electron image before the peel test, and (b) is the secondary electron image after the peel test corresponding to (a). It is an electronic image. Both were obtained with an acceleration voltage of 0.5 kV. The brightness values of these images were digitized to determine the brightness values of Sample A in Table 1. The brightness values were similarly obtained for samples B and C.

  FIG. 7 is a diagram showing a result of dividing the brightness value of each point in FIG. 6B by that in FIG. 6A. In the flat part, the area where the film is peeled is represented by dark contrast, and the distribution of the area where the film is peeled is clearly shown.

  The present invention can be used for evaluating the adhesion of a thin film formed on the surface of a substrate, for example, a thin film having a thickness of several nm or more. The present invention can be suitably used for evaluating the adhesion of a material formed with a thin film made of an oxide film on a semiconductor or metal, particularly in the field of semiconductor materials and steel materials.

  According to the present invention, since SEM can be used, it is possible to evaluate the adhesion of the film thickness within a few tens of nanometers in the plane and visualize the peeled portion. It can be used to evaluate the adhesion of thin films.

  The present invention can be used not only for the development of the product as described above, but also for product management and shipping management of the product, and also for feedback to the adjustment of the manufacturing conditions of the manufacturing process for manufacturing the product.

In this invention, it is a schematic diagram which shows the mechanism which can visualize the existence part of a thin oxide film layer, (a) explains the secondary electron emission in normal acceleration voltage, (b) shows the acceleration voltage of incident electrons after incidence. The secondary electron emission when the low acceleration voltage is selected so that the diffusion of electrons in the film material is contained will be described. It is a schematic diagram showing a change in the amount of secondary electrons generated with respect to the acceleration voltage when the acceleration voltage is changed from a higher one to a lower one in a sample having a low-conductivity film having a different thickness on the surface. It is a figure which shows the relationship between the acceleration voltage and film thickness which the generation amount of the secondary electron starts when the acceleration voltage is changed from the higher one to the lower one. It is a figure which shows the relationship between a secondary electron generation amount and film thickness when an electron beam is irradiated with the predetermined acceleration voltage lower than the acceleration voltage which the generation amount of a secondary electron starts decreasing. It is a figure explaining the method of evaluating adhesiveness based on the relationship between the amount of secondary electron generation, and film thickness. FIG. 2 is a micrograph for a drawing showing a secondary electron image of the surface of the sample A of Example 1 before and after the peeling test, (a) is a secondary electron image before the peeling test, and (b) is a portion corresponding to (a). It is a secondary electron image after a peeling test. For the sample A of Example 1, the brightness value at each point in FIG. 6B (the brightness value after the peel test) is the brightness value at each point in FIG. 6A (the brightness value before the peel test). In the photomicrograph for the drawing, which shows the result of dividing by (), the area where the film peeled is shown in dark contrast.

Claims (8)

(1) A step of irradiating a sample surface having a thin film on the surface with an electron beam at a predetermined acceleration voltage selected according to the film thickness, and measuring the amount of secondary electrons;
(2) a step of performing a peel test on the sample;
(3) irradiating the surface of the sample after the peel test with an electron beam at the predetermined acceleration voltage and measuring the amount of secondary electrons;
(4) A step of obtaining a difference between a measured value of the amount of secondary electrons before the peel test and a measured value of the amount of secondary electrons after the peel test;
(5) A step of evaluating the adhesion of the thin film based on the difference in the measured value of the amount of secondary electrons before and after the peel test;
A method for evaluating the adhesion of a thin film, comprising: (1) The surface of a sample having a thin film on the surface is irradiated with an electron beam at a predetermined acceleration voltage selected according to the film thickness, the secondary electron image is observed, and the amount of secondary electrons is A process of digitizing the brightness value;
(2) a step of performing a peel test on the sample;
(3) The surface of the sample after the peel test is irradiated with an electron beam at the predetermined acceleration voltage, the secondary electron image is observed, and the secondary electron quantity is quantified as a brightness value of the secondary electron quantity. Process,
(4) obtaining a difference between the brightness value of the secondary electron amount before the peel test and the brightness value of the secondary electron amount after the peel test;
(5) a step of evaluating the adhesion of the thin film based on the difference in brightness value of the amount of secondary electrons before and after the peel test;
A method for evaluating the adhesion of a thin film, comprising: In Claim 1, the electron beam irradiated to the sample surface is irradiated while scanning on the sample surface, and the amount of secondary electrons corresponding to the electron beam irradiation position before and after the peeling test is measured, respectively. From the difference between the measured value of the amount of secondary electrons before the peel test corresponding to the irradiation position and the amount of secondary electrons after the peel test, it is characterized by evaluating the adhesion of the thin film at each position on the sample surface, Evaluation method of adhesion of thin film. The brightness value of the amount of secondary electrons corresponding to the electron beam irradiation position before and after the peeling test is irradiated with the electron beam irradiated on the sample surface while scanning the surface of the sample. From the difference between the brightness value of the secondary electron quantity before the peel test corresponding to the electron beam irradiation position and the brightness value of the secondary electron quantity after the peel test, the adhesion of the thin film at each position on the sample surface was determined. A method for evaluating adhesion of a thin film, characterized by evaluating. 5. The method for evaluating adhesion of a thin film according to claim 1, wherein the acceleration voltage of the electron beam applied to the sample surface is in the range of 0.01 kV to 2 kV. 6. The method for evaluating adhesion of a thin film according to claim 1, wherein the thin film comprises an oxide and / or a hydroxide on a metal or a semiconductor. The manufacturing process which forms a thin film on the surface of a base material, and the adhesiveness of a thin film with the method in any one of Claims 1-6 with respect to one part or all part of the base material which formed the thin film on the surface at the said manufacturing process A method for producing a substrate having a thin film on the surface thereof. In advance, the correspondence between the difference in the amount of secondary electrons before and after the peel test and the adhesion or the correspondence between the difference in the brightness value of the amount of secondary electrons before and after the peel test and the adhesion, and the evaluation step, Correspondence between the difference in secondary electron amount before and after the peel test and adhesion, the difference in measured value of the secondary electron amount before and after the peel test in the evaluation step, or the brightness of the secondary electron amount before and after the peel test Determining whether or not the thin film has a predetermined adhesion based on the correspondence between the difference in thickness and the adhesiveness, and the difference in the brightness value of the amount of secondary electrons before and after the peel test in the evaluation step. The manufacturing method of the base material which has a thin film on the surface of Claim 7 characterized by these.

Images